27,256 research outputs found
Implementation of elastic-plastic structural analysis into NASTRAN
Elastic-plastic analytic capabilities were incorporated into the NASTRAN program. The present implementation includes a general rigid format and additional bulk data cards as well as to two new modules. The modules are specialized to include only perfect plasticity of the CTRMEN and CROD elements but can easily be expanded to include other plasticity theories and elements. The practical problem of an elastic-plastic analysis of a ship's bracket connection is demonstrated and compared to an equivalent analysis using Grumman's PLANS program. The present work demonstrates the feasibility of incorporating general elastic-plastic capabilities into NASTRAN
Correlation between magnetic and transport properties of phase separated LaCaMnO
The effect of low magnetic fields on the magnetic and electrical transport
properties of polycrystalline samples of the phase separated compound
LaCaMnO is studied. The results are interpreted in the
framework of the field induced ferromagnetic fraction enlargement mechanism. A
fraction expansion coefficient af, which relates the ferromagnetic fraction f
with the applied field H, was obtained. A phenomenological model to understand
the enlargement mechanism is worked out.Comment: 3 pages, 3 figures, presented at the Fifth LAW-MMM, to appear in
Physica B, Minor change
Different steady states for spin currents in noncollinear multilayers
We find there are at least two different steady states for transport across
noncollinear magnetic multilayers. In the conventional one there is a
discontinuity in the spin current across the interfaces which has been
identified as the source of current induced magnetic reversal; in the one
advocated herein the spin torque arises from the spin accumulation transverse
to the magnetization of a magnetic layer. These two states have quite different
attributes which should be discerned by current experiments.Comment: 8 pages, no figure. Accepted for publication in Journal of Physics:
Condensed Matte
Data processing method for a weak, moving telemetry signal
Method of processing data from a spacecraft, where the carrier has a low signal-to-noise ratio and wide unpredictable frequency shifts, consists of analogue recording of the noisy signal along with a high-frequency tone that is used as a clock to trigger a digitizer
Magnetoresistive memory in phase separated LaCaMnO
We have studied a non volatile memory effect in the mixed valent compound
LaCaMnO induced by magnetic field (H). In a previous work
[R.S. Freitas et al., Phys. Rev. B 65 (2002) 104403], it has been shown that
the response of this system upon application of H strongly depends on the
temperature range, related to three well differentiated regimes of phase
separation occurring below 220 K. In this work we compare memory capabilities
of the compound, determined following two different experimental procedures for
applying H, namely zero field cooling and field cooling the sample. These
results are analyzed and discussed within the scenario of phase separation.Comment: 4 pages, 2 figure
Lateral diffusive spin transport in layered structures
A one dimensional theory of lateral spin-polarized transport is derived from
the two dimensional flow in the vertical cross section of a stack of
ferromagnetic and paramagnetic layers. This takes into account the influence of
the lead on the lateral current underneath, in contrast to the conventional 1D
modeling by the collinear configuration of lead/channel/lead. Our theory is
convenient and appropriate for the current in plane configuration of an
all-metallic spintronics structure as well as for the planar structure of a
semiconductor with ferromagnetic contacts. For both systems we predict the
optimal contact width for maximal magnetoresistance and propose an electrical
measurement of the spin diffusion length for a wide range of materials.Comment: 4 pages, 3 figure
Transport in superlattices on single layer graphene
We study transport in undoped graphene in the presence of a superlattice
potential both within a simple continuum model and using numerical
tight-binding calculations. The continuum model demonstrates that the
conductivity of the system is primarily impacted by the velocity anisotropy
that the Dirac points of graphene develop due to the potential. For
one-dimensional superlattice potentials, new Dirac points may be generated, and
the resulting conductivities can be approximately described by the anisotropic
conductivities associated with each Dirac point. Tight-binding calculations
demonstrate that this simple model is quantitatively correct for a single Dirac
point, and that it works qualitatively when there are multiple Dirac points.
Remarkably, for a two dimensional potential which may be very strong but
introduces no anisotropy in the Dirac point, the conductivity of the system
remains essentially the same as when no external potential is present.Comment: 8 pages, 7 figures, submitted to Phys. Rev.
Galilean Limit of Equilibrium Relativistic Mass Distribution
The low-temperature form of the equilibrium relativistic mass distribution is
subject to the Galilean limit by taking In this limit
the relativistic Maxwell-Boltzmann distribution passes to the usual
nonrelativistic form and the Dulong-Petit law is recovered.Comment: TAUP-2081-9
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